ABSTRACT A disturbingly high number of young children around the world experience stunted growth and development with irreparable consequences through the lifespan. Recent estimates show 250 million children less than five years of age are not reaching their developmental potential, and 151 million have stunted growth.1,2 Determinants of stunted growth and development are multi-factorial, including interactions between biological, behavioral, social, and environmental conditions, yet the evidence-base is minimal for integrated approaches to tackle the interwoven factors. Our group recently found significant impacts from an egg intervention on young child growth and biomarkers of nutrition and brain development. The effects on important psychosocial indictors of child development, however, were not assessed. Building on these findings and those of our pilot study of a group-based, multicomponent intervention (Grandi Byen, Haitian Creole for ?grow well?), we propose a larger RCT to examine a greater breadth of egg intervention outcomes, the synergistic effects of adding psychoeducational parenting to the egg intervention, and mediating biological, behavioral and social factors. The 3-arm longitudinal RCT, to be carried out in Cap-Haitien, Haiti, where our group has nine years of research experience, established partnerships, and a strong research infrastructure. It is representative of resource-poor urban contexts globally, where parents face common economic and environmental challenges to child growth and development. The trial will compare the following groups for effectiveness in reducing young child stunted growth and enhancing overall development: 1) multicomponent Grandi Byen intervention (responsive parenting, nutrition, hygiene + one egg per day for 6 months); 2) nutrition intervention (one egg per day for 6 months); and 3) standard well-baby care. Infants will be enrolled between 6-8 months of age and followed longitudinally for one year. The specific aims are: Aim 1 (primary): To demonstrate the reproducibility and feasibility of egg-based interventions in reducing childhood stunting, and test its impact on development. Hypothesis 1: Linear growth will be increased by 0.30 LAZ in children receiving one egg per day compared to standard care. Hypothesis 2: Children receiving the egg intervention will have better cognitive, motor and language development compared to standard care. Question 1 (exploratory): Does an egg-based intervention impact social-emotional development? Aim 2 (primary): To investigate the incremental benefit of Grandi Byen compared to egg only and standard care groups on primary outcomes of child growth and development. Hypothesis 3: Children of mothers receiving Grandi Byen will increase linear growth by 0.10 LAZ compared to the egg intervention. Hypothesis 4: Children of mothers receiving Grandi Byen will have higher scores on child cognition, language, motor, and socio-emotional development, with an effect size of 0.36 on cognition, compared to standard care. An economic evaluation will be conducted to compare the efficiency of the interventions. Aim 3 (secondary). To explore pathways of intervention impacts on child growth and development by delineating the additive and synergistic effects of biological (nutrient biomarkers, bone age, and enteric disease), psychosocial (responsive parenting, cognitive stimulation), and environmental (hygiene and sanitation, diet) factors. This study expands upon this earlier work by bringing together a transdisciplinary team spanning the biological and social sciences to work in partnership with Haitian collaborators. We will merge methods and concepts to produce comprehensive perspectives on several high priority areas including social, economic and biological factors that impact child brain development and function, nutrition among infants and very young children, determinants of bone health; and traumatic stress associated with growing up in abject poverty.